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1

Experimental investigation for the local scour around V-shaped spur-dikes

Alasadi Layth Abdul Rasool, Khlif Tagreed Hameed, Hassan Fadhel Abdulabbas

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2023

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Vol. 32, No. 1

68--86

EN

Spur-dikes are efficient hydraulic structures that are made for numerous purposes. They have one end on the stream bank and another extending into the current. As a result of the existing spur-dikes in the stream course, the local scour phenomena usually occur around them, leading to several predicaments which have been of great concern to the hydraulic engineers. For the present work, laboratory experiments were carried out to measure the scour depths around several spur-dikes located at different distances for the V-shaped one. The experiments were conducted using physical models installed in a non-curved flume with a bed with uniform cohesion-less sediment of a medium particle size (d50 = 0.7 mm). All the models were operated under the subcritical flow of clear-water conditions. The investigations include three spur-dikes (1, 2 and 3) and three distances between them (1, 1.5 and 2 of spur-dike length) as two countermeasures to minimize the local scour depths. The results showed that an increasing number of spur-dikes and the distances between them would decrease the scour depths within the limit of the present study. The experimental data were used to create a new formula of R = 0.954 that reflects a good agreement with the experimentally observed results.

2

Experimental investigation of local scour under two oblong piers of a bridge crossing a sharp bend river

Abdulwahd Abdulrazaq K., Maatooq Jaafar S.

Journal of Water and Land Development

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2023

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no. 58

129--135

EN

Bridges built across a river bend and supported by more than one pier has been experimentally studied regarding the shape and nature of erosion and deposition. For this purpose, a U-shaped laboratory channel was used with two oblong piers installed at different locations. The first one was at the mid-section of the upstream straight reach, whereas in the second site within the bend, the piers have been installed at sections of central angles 0°, 30°, 60°, 90°, 120°, 150°, 170°, and 180°, from the beginning to the end of the bend segment respectively. The studies were conducted under clear water and threshold flow conditions. The results show that the higher and lower values of local scour around the pier positioned close to the outer bank, are 1.803 and 0.623 times the pier width when the bridge was installed at an angle of 90° and 30° respectively. As for the pier close to the inner bank, the deepest local scour was 1.786 times of the pier width when the bridge was installed at 60° of the bend, while the least one was 0.516 times of the pier width when the bridge was located in the 180° sector. It is worth noting that the presence of piers within sector 150 is less affected by local scour than in the other sections.

3

Bridge headwater afflux estimation using bootstrap resampling method

Kiraga Marta, Bajkowski Sławomir, Urbański Janusz

Archives of Civil Engineering

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2023

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Vol. 69, nr 1

21--37

EN

The bridge structure’s development causes a riverbed cross-sections contraction. This influences the flow regime, being visible during catastrophic floods. Then the flow velocity increases and water piles up upstream the bridge, where headwater afflux could be observed. These changes depend on the watercourse geometry and the bridge cross-section properties, especially on the degree of flow contraction under the bridge. Hydraulic conditions under the bridge depend on flow velocity, dimensions, and shape of abutments, the granulometric composition of bedload, which can be quantitatively characterized by hydraulic resistance coefficients. The research subject of headwater afflux is equated with the recognition of morphodynamic processes occurring along the passage route. The headwater afflux could be estimated by empirical formulas and by the energy method using Bernoulli’s law. Empirical methods are optimized by adopting various statistical criteria. This paper compares the headwater afflux values calculated using two existing empirical formulas, Rehbock and Yarnell, and compares them with the results of laboratory tests. Following the assumption that the free water surface is influenced by flow resistance, an attempt was made to include friction velocity in the empirical formulas. Based on the Authors’ database, the coefficients used were optimized using bootstrap resampling in Monte Carlo simulation. The analyses demonstrated that the formula best describing the phenomenon of headwater afflux upstream the bridge is an empirical formula built based on the historical Yarnell formula, which includes friction velocity value. The optimized equation provides an average relative error of 12.9% in relation to laboratory observations.

PL

Zabudowanie koryta rzeki filarami i przyczółkami mostu powoduje zwężenie jego przekroju. Wpływa to zmiany warunków przepływu, które widoczne są przede wszystkim podczas wezbrań katastrofalnych. Następuje wtedy zwiększenie prędkości przepływu oraz spiętrzenie wody przed mostem. Zmiany te zależą od geometrii koryta cieku oraz przekroju mostowego, a szczególnie stopnia zwężenia strumienia pod mostem. Warunki hydrauliczne pod mostem zależą od prędkości przepływu, wymiarów i kształtu podpór, składu granulometrycznego rumowiska, które scharakteryzować można ilościowo za pomocą współczynników oporów hydraulicznych. Tematyka badawcza spiętrzenia pod mostem stawiana jest na równi z rozpoznaniem procesów morfodynamicznych zachodzących na długości przeprawy. Spiętrzenie pod mostami określa się wzorami empirycznymi oraz metodą energetyczną wykorzystującą prawo Bernoulliego. Metody empiryczne optymalizuje się przyjmując różne kryteria statystyczne. W artykule porównano spiętrzenie pod mostem obliczone za pomocą dwóch znanych formuł empirycznych Rehbocka oraz Yarnella i porównano je z wynikami badań laboratoryjnych. Kierując się przesłanką, że na ukształtowanie swobodnego zwierciadła wody w rejonie mostu wpływają także opory przepływu, podjęto próbę włączenia prędkości dynamicznej do formuł empirycznych. Na podstawie własnej bazy danych współczynniki wykorzystanych formuł zoptymalizowano z użyciem metody bootstrap resampling w symulacji Monte Carlo. Przeprowadzone analizy wykazały, że formułą najlepiej opisującą zjawisko spiętrzenia pod mostem jest formuła empiryczna zbudowana na podstawie historycznej formuły Yarnella. Uwzględniając w niej prędkość dynamiczną i optymalizując uzyskano średni błąd względny 12.9%. Taka wartość średniego błędu względnego potwierdza słuszność przyjętego podziału pola prędkości na odpływie. Stwierdzono, że metoda bootstrap resampling w symulacji Monte Carlo stanowi użyteczne narzędzie inżynierskie przy optymalizacji formuł w badaniach hydraulicznych. Szczególnie cennym elementem artykułu jest wykorzystywanie próby danych historycznych.

4

The study of the local scour behaviour due to interference between abutment and two shapes of a bridge pier

Muhsen Noor A.A., Khassaf Saleh I.

Journal of Water and Land Development

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2022

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no. 55

240--250

EN

Although the complexities and irrevocable consequences associated with bridge scour have attracted researchers interest, their studies scarcely indicated the effect of a bridge pier proximity to an abutment. This research aims to measure maximum scour depth and exhibit the impact of pier-abutment scour interference based on laboratory experiments where vertical-wall abutment and two shapes of a pier (oblong and lenticular) were used at three different spacings (23.5, 16.0, 9.0 cm). The results showed an obvious increase in the scour depth ratio when increasing flow intensity, Froude number, and a decreasing flow depth. They also showed that reduced pier-abutment spacing was accompanied by increase in pier scour for both shapes while decrease in abutment scour. The maximum scour depth that caused by an oblong shape was more than a lenticular shape by about 10.8%. Furthermore, new empirical equations were derived using IBM SPSS Statistics 21 with determination coefficients of 0.969, 0.974, and 0.978 for oblong, lenticular and abutment, respectively. They showed the correlation between predicted and observed data.

5

Artificial Neural Network for Estimation of Local Scour Depth Around Bridge Piers

Shakir Ali Ali Ahmed, Günal Mustafa

Archives of Hydro-Engineering and Environmental Mechanics

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2021

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Vol. 68, nr 2

87--101

EN

Local scour around bridge piers impairs the stability of bridges’ structures. Therefore, a delicate estimation of the local scour depth is vital in designing the bridge piers foundations. In this research, MATLAB software was used to train artificial neural network (ANN) models with four hundred laboratory datasets from different laboratory studies, including five parameters: pier diameter, flow depth flow velocity, critical sediment velocity, sediment particle size, and equilibrium local scour depth. The outcomes present that the ANN model with the Levenberg-Marquardt algorithm and 11 nodes in the single hidden layer gives an accurate estimation better than other ANN models trained with different training algorithms based on the regression results and mean squared error values. Besides, the ANN model accurately provides predicted local scour depth and is better than linear and nonlinear regression models. Furthermore, sensitivity analysis shows that removing pier diameter from training parameters diminishes the reliability of prediction.

6

Study the local scour around different shapes of single submerged groyne

Rashak Budoor M., Khassaf Saleh I.

Journal of Water and Land Development

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2020

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no. 47

1--9

EN

River training structures; such as submerged groynes are low profile linear structures that are generally located on the outside bank to form groynes fields and prevent the erosion of stream banks by keeping a flow away from it. In the present research, the maximum scour depth was measured based on laboratory experiments where different shapes of submerged groynes (I-shape, L-shape, T-shape) were used as sort of countermeasures to investigate about most shapes that reduce the scour around them. The result of submerged groynes showed a clear decrease in scour depth ratio due to increasing submerged ratio and increase the scour hole geometry with increasing of flow intensity, and also Froude number. The maximum scour hole in this research was observed at T-shape groyne and then followed by I-shape groyne and L-shape groyne. The maximum scour depth that cased by I-shape was more than L-shape by a percentage about 8.2%, and it was less than T-shape by a percentage about 16.4%.

7

Interference of an upstream pier on local scour at downstream piers

Khaple S., Hanmaiahgari P. R., Gaudio R., Dey S.

Acta Geophysica

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2017

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Vol. 65, no. 1

29--46

EN

In this study, three kinds of pier arrangements were tested. They are (i) two piers in tandem, (ii) two piers in staggered arrangement, and (iii) three piers in symmetrically staggered arrangements. In the arrangement of two piers in tandem, the equilibrium scour depth at downstream pier decreases with an increase in downstream distance up to approximately eight times pier diameter and then increases with further increase in downstream distance. However, the scour depth at downstream pier is always smaller than that at upstream pier. In the arrangement of two staggered piers, the scour depth at the downstream pier for L/b = 4, where L is the offset distance and b is the pier diameter, is the same as that of the upstream pier at S = 8b, where S is the streamwise spacing or distance between piers. Further, for three piers in staggered arrangement, as the lateral spacing between downstream piers increases, the equilibrium scour depth at downstream pier decreases.

8

3D numerical simulation of flow field around twin piles

Amini A., Parto A. A.

Acta Geophysica

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2017

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Vol. 65, no. 6

1243--1251

EN

In this study to identify the flow pattern and local scour mechanism around pile groups, the flow field was simulated using FLOW-3D software. A pair of pile on a flat-bed channel with side by side and tandem arrangements was investigated. To establish Navier–Stokes equations, the RNGk-ε turbulence model was used and the results were verified using experimental data. In case of FLOW-3D capability, it was found that the software was able to properly simulate the expected interaction between the pile groups. The results of flow field simulation showed that Reynolds number and the pile spacing are the most influential variables in forming vortices. The flow around tandem pile and the downward flow around wake vortices were more intense and complicate in comparison with side by side arrangements and single pile.

9

On Flow-Altering Countermeasures for Scour at Vertical-Wall Abutment

Radice A., Lauva O.

Archives of Hydro-Engineering and Environmental Mechanics

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2012

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Vol. 59, nr 3-4

137-153

EN

Results are presented for clear-water scour experiments at a vertical-wall abutment where the obstacle was modified with slots or roughening elements as flow-altering countermeasures against the erosion process. The laboratory campaign comprehended an initial experiment with an unprotected obstacle, two experiments with slots above and beneath the non-scoured bed level, respectively, and one experiment with a roughened abutment. The repeatability of the experiments was checked and found satisfactory. The measured data set consisted of (i) scour depth with time; (ii) geometry of the erosion hole; and (iii) sediment motion pattern at several evolution stages of the process. A novel feature of the work was the attempt to combine evidence on the scour depth and that on sediment motion so as to shed light on the mechanism of scour reduction by the countermeasures tested. It is argued that this strategy might furnish guidelines for future extensive investigations of scour countermeasures, aimed at finding optimal design solutions.

10

Rozkłady prędkości przepływu na długości rozmycia w dolnym stanowisku na modelu jazu

Urbański J.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2010

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Vol. 19, No. 1

34--42

PL

W pracy przedstawiono wyniki badań laboratoryjnych, których celem było rozpoznanie rozkładów prędkości przepływu na długości rozmycia na modelu jazu. Model budowli z wypływem wody spod zasuwy, niecką do rozpraszania energii i płaskim umocnieniem wykonano w korycie o przekroju prostokątnym. Jako materiał rozmywalny wykorzystano piasek sortowany o d50=1,1mm. Przeprowadzono analizę wyników pod kątem rozpoznania zmienności rozkładów prędkości wraz z pogłębianiem się wyboju w czasie Rozkłady prędkości mają zróżnicowany kształt, który związany jest z miejscem położenia pionu pomiarowego w obrębie wyboju. Nad obniżającym się stokiem rozmycia za umocnieniem rozwija się walec wodny, który w dużym stopniu determinuje rozkład prędkości w tworzącym się wyboju.

EN

The paper presents results of laboratory tests, purpose was to recognize distributions of flow velocity in the local scour. Investigations were conducted on model of weir with overflow under closure, bottom of water basins, horizontal bed protection in downstream and scouring area. As eroded material on model sorted sand was used with d50=1,1mm. Results analysis was conducted in order to establish changing of velocity profiles during increase of scour depth. Distributions of velocity have different shape. Profiles of velocity depend on the location of measuring place in the local scour. Below the bed protection the roller with horizontal axis is formed. It has a decisive influence on the velocity distribution in the local scour.

11

Wpływ hydraulicznych warunków przepływu na modelu jazu na głębokość rozmycia lokalnego

Urbański J.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2009

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Vol. 18, No. 2

21--29

PL

W artykule przedstawiono wyniki badań kształtowania się lokalnego rozmycia dna w czasie trwania przepływu na modelu jazu. Model budowli z wypływem wody spod zasuwy, z niecką do rozpraszania energii i płaskim umocnieniem wykonano w korycie o przekroju prostokątnym. Jako materiał rozmywalny wykorzystano piasek sortowany o d50=1,1mm. Celem badań było rozpoznanie zmienności rozmiarów wyboju w czasie trwania przepływu w różnych warunkach hydraulicznych. Głębokość strumienia w stanowisku dolnym ma wpływ na ostateczny kształt rozmycia i maksymalną głębokość wyboju. Zwiększanie napełnienia koryta w dolnym stanowisku powoduje wzrost współczynnika zatopienia odskoku, a następstwem tego jest ograniczenie głębokości rozmycia.

EN

Paper presented results of investigation of formation local scour on the model of weir. Investigations were conducted on model with overflow under closure, bottom of water basins, horizontal bed protection in downstream and washing-out area. As eroded material on model sorted sand was used with d50 = 1.1 mm. Purpose of investigation were recognition variability dimension of scour during of discharge for different flow condition. Investigations showed influence depth of downstream on depth of scour, influence velocity of stream on eroded process.

12

Zmiany uziarnienia na dnie poniżej budowli piętrzącej

Zawadzki P., Hämmerling M.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2008

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Vol. 17, No. 2

146--154

EN

The paper presents results of laboratory investigations of local scour in non-uniform non-cohesive bed material below a horizontal solid apron. An experiment of local scouring conducted in a glass-sided rectangular fl ume under clear-water conditions with constant water discharge was performed. In this study several non-uniform soils consisted of the following coloured fractions: 0.5-1.25, 1.25-2.5, 2.5-4.0, 4.0-6.3, and 6.3-10.0 mm were used. Every scour hole had begun just below the solid apron having mild slope and downward concave shape. Similar changes in grain composition were observed in all tests; the hole bottom at the deepest section was covered by the largest grains. During the experiments it was found that bed armour coat had formed in soils with standard deviation of mean grain size σg > 2 and downstream of the maximum scour hole depth, only. Soils with σg < 2 did not create any armour coat, and single coarse grains increased turbulence behind them and accelerated erosion of finer grains.

13

Wpływ szorstkości umocnień w dolnym stanowisku jazu na lokalne rozmycia dna

Urbański J.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2008

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Vol. 17, No. 2

169--177

EN

In paper are presented investigation results of scour downstream of weir for different roughness of bed protection. Investigations were conducted on model construction with stilling pool and horizontal bed protection about 1.0 m long. The bed protection in downstream was made as concrete and as riprap with relative roughness k = 0.028. As bed material in experiments was used sand (d50 = 1.1 mm, (d84/d16)0.5 = 1.77). In result of use rip-rap as bed protection downstream obtained reduction of velocity and turbulence intensity of stream near the bed on the length in downstream. It was influence on decrease of sizes of local scour.

14

Kształtowanie się rozmyć na modelu jazu ze zmienną wysokością piętrzenia

Urbański J.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2006

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Vol. 15, No. 1

29--37

EN

Paper presented analysis results of investigations of model on formation of scour in time. Investigations were conducted on model taired constructions with the over of water under the closure, bottom of water basins and washing-out area. Model were made in scale 1 : 30. In inwestigations were used as eroded material - sand (d50=1,1 mm). For modelling hydraulic parameters of flow on model were used to Froude’a criterion. Purpose of investigations was recognition of variability of sizes and of shape of scour during of flow in different hydraulic parameters of flow and at variable headwater on the model. Investigations showed that with increase of headwater on the model is observed increase of dimensions of scour.

15

Rozwój miejscowego rozmycia w czasie na modelach jazu w dwóch skalach

Urbański J.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2005

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Vol. 14, No. 1

67--75

EN

Paper presented analysis results of investigations of influence scale model on formation of scour in time. Investigations were conducted on two model this same taired constructions with the over of water under the closure, bottom of water basins and washing-out area. Models were made in two skales 1 : 30 and 1 : 55. In inwestigations were used this same eroded materiał on two models - sand. Estimated change of parameter for morfological time scale between two models of the dam. In Froudian models with a nonlinearly scaled size of sand grains the maximum depth of local scour develop slower than their linear counterparts in prototypes, except for the initial stage of scour.

16

Local scour in non-uniform bed material below a horizontal solid apron

Zawadzki P., Błażejewski R.

Archives of Hydro-Engineering and Environmental Mechanics

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2001

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Vol. 48, nr 1

3-17

EN

A two-dimensional mathematical model of local scour in non-uniform non-cohesive soil below a horizontal solid apron is presented. The model parameters were identified on the basis of own experimental laboratory data. Verification of the model, accomplished using other laboratory data, showed fairly good conformity, however, additional verification under field conditions is needed.